Pigment mixture

ABSTRACT

The present invention relates to pigment mixtures consisting of at least two components, component A being Sio 2  flakes coated with one or more metal oxides and/or metals and component B being special-effect pigments, and to their use in varnishes, paints, printing inks, masterbatches, plastics and cosmetic formulations.

The present invention relates to pigment mixtures consisting of at least two components, component A being SiO₂ flakes coated with one or more metal oxides and/or metals and component B being one or more coated or uncoated special-effect pigments, and to their use in varnishes, paints, printing inks, plastics and cosmetic formulations.

With platelet-shaped pigments, hiding power and gloss are often difficult to realize simultaneously to a satisfactory extent. For instance, SiO₂ flakes or mica platelets covered with one or more thin metal oxide layers feature interference colors and a high luster but at the same time, owing to the transparent substrate, feature high transparency and hence a comparatively poor hiding power.

Thus EP 0 562 329 discloses a pigment mixture comprising iron oxide-coated aluminum flakes in combination with iron oxide-coated mica pigments.

DE-A-42 40 511 discloses a pigment mixture which consists of an interference pigment and a platelet-shaped color pigment. The interference pigment comprises metal oxide-coated mica flakes or SiO₂ flakes, and the color pigment can be colored, uncoated SiO₂ flakes. This pigment mixture is incorporated into coating materials, printing inks or plastics.

The object of the present invention is to provide a pigment mixture which is notable for relatively high hiding power and which lends itself well to incorporation into the respective system in which it is used, and for which at the same time a separation of pigment/colourant in the system is largely ruled out.

Surprisingly, a pigment mixture has now been found which has none of the disadvantages indicated above. The pigment mixture of the invention consists of at least two components, component A being SiO₂ flakes coated with one or more metal oxides and/or metals and component B being one or more special-effect pigments. The admixture of the special-effect pigments to the coated SiO₂ flakes is able to give the systems in which they are used a multiple flop, the color effect is intensified, and new color effects are achieved.

The invention thus provides a pigment mixture consisting of at least two components, component A being SiO₂ flakes coated with one or more metal oxides and component B being one or more special-effect pigments.

The invention likewise provides the formulations, such as paints, varnishes, printing inks, plastics, agricultural films and cosmetic formulations, which comprise the pigment mixture of the invention.

The coated SiO₂ flakes can be mixed in any proportion with the special-effect pigments. The ratio of component A to component B is preferably from 1:10 to 10:1, in particular from 3:1 to 5:1.

The SiO₂ flakes preferably produced on a continuous belt in accordance with WO 93/08237 are based on a platelet-shaped, transparent matrix and generally possess a thickness of between 0.1 and 5 μm, in particular between 0.2 and 2.0 μm. The extent in the two other dimensions is usually between 1 and 250 μm, preferably between 2 and 100 μm and, in particular, between 5 and 40 μm. The SiO₂ flakes are provided with one or more metal oxide layers and/or metal layers. Examples of suitable metal oxides or metal oxide mixtures are titanium dioxide, zirconium oxide, zinc oxide, iron oxides and/or chromium oxide, especially TiO₂ and/or Fe₂O₃. The SiO₂ flakes can be coated as described, for example, in WO 93/08237 (wet chemical coating) or DE-A-196 14 637 (CVD process).

Instead of the outer metal oxide layer a semitransparent layer of metal can be used. Suitable metals for this are, for example, Cr, Ti, Mo, W, Al, Cu, Ag, Au and Ni. Prefered pigments have the following layer structure: SiO₂ flakes+metal+SiO₂+metal oxide.

To induce special colour effects, fine particles in the nanometre size range can be incorporated additionally into the metal oxide layers of high or low refractive index. Examples of suitable candidates are finely divided TiO₂ or finely divided carbon (carbon black) with particle sizes in the range 10-250 nm. A controlled influence can be exerted on luster and hiding power by virtue of the light-scattering properties of such particles. Preferably, the SiO₂ flakes are coated with one or more metal oxides.

Suitable components B for the pigment mixture of the invention are all special-effect pigments familiar to the skilled worker in the effect pigment sector, examples being metal effect pigments, such as aluminum, copper, zinc, tin and their alloys. Aluminum and gold bronze alloys are preferably to be mentioned, especially those having a particle size of from 2 to 40 μm. The pigment mixtures of the invention preferably comprise coated platelet-shaped iron oxide, aluminum flakes or coated aluminum flakes. Special-effect pigments of this kind are marketed by BASF under the name Paliocrom®, by Eckart-Werke under the name Standard®, and by the company Flex. Mention should also be made of pearl luster pigments, Al₂O₃ flakes coated with metal oxides, such as TiO₂ or Fe₂O₃, for example, graphite platelets, BiOCl or glass flakes.

Pearl luster pigments, mica flake pigments coated with one or more metal oxides, are obtainable, for example, from Merck KGaA, Darmstadt, under the trade name Iriodin®. The latter pigments are known, for example, from the German Patents and Patent Applications 14 67 468, 19 59 998, 20 09 566, 22 14 545, 22 15 191, 22 44 298, 23 13 331, 25 22 572, 31 37 808, 31 37 809, 31 51 343, 31 51 354, 31 51 355, 32 11 602 and 32 53 017. Mica pigments coated with TiO₂ and/or Fe₂O₃ are employed in particular. As phyllosilicate both natural and synthetic mica are suitable.

The pigment mixture of the invention is simple and easy to handle. The pigment mixture can be incorporated into the system in which it is used by simple stirring. Laborious milling and dispersing of the pigments is not necessary.

The pigment mixture of the invention can be used for pigmenting coating materials, printing inks, plastics, agricultural films, button pastes, for the coating of seed, for the colouring of food, coatings of medicaments or cosmetic formulations. The concentration of the pigment mixture in the system in which it is to be used for pigmenting is generally between 0.01 and 50% by weight, preferably between 0.1 and 5% by weight, based on the overall solids content of the system. This concentration is generally dependent on the specific application.

Plastics comprising the pigment mixture of the invention in amounts of from 0.1 to 50% by weight, in particular from 0.5 to 7% by weight, are frequently notable for a particular sparkle effect.

In the coating sector, especially in automotive finishing, the pigment mixture is employed in amounts of 0.5-10% by weight. The proportion in which the coated SiO₂ flakes are mixed with component B, especially coated or uncoated aluminum flakes, depends on the desired effect. The SiO₂ flakes are preferably employed with component B in a ratio of 5:1, in particular of 3:1. In the coating material, the pigment mixture of the invention has the advantage that the desired colour flop effect is obtained by a single-layer coating (one-coat systems or as a basecoat in a two-coat system). This colour flop is extremely pronounced even under diffuse light. In comparison with coatings which comprise an interference pigment rather than the coated SiO₂ flakes, coatings with the pigment mixture of the invention exhibit a marked depth effect and a glitter effect and also a strong colour flop.

In the pigmentation of binder systems, for example for paints and printing inks for intaglio, offset or screen printing, pigment mixtures consisting of coated SiO₂ flakes with Stapa®—aluminum and gold bronze pastes from Eckart-Werke—have proven particularly suitable. The pigment mixture is incorporated into the printing ink in amounts of 2-50% by weight, preferably 5-30% by weight and, in particular, 8-15% by weight. The mixing ratio of component A to component B is preferably in the range from 1:10 to 10:1. The printing inks comprising the pigment mixture of the invention exhibit purer hues and are of improved printability owing to the good viscosity values.

The invention likewise provides pigment preparations comprising coated or uncoated SiO₂ flakes, metal effect pigments, binders and, if desired, additives, the said preparations being in the form of substantially solvent-free, free-flowing granules. Such granules contain up to 95% by weight of the pigment mixture. A pigment preparation in which the pigment mixture of the invention is pasted up with a binder and with water or an organic solvent, with or without additives, and the paste is subsequently dried and brought into a compact particulate form, e.g. granules, pellets, briquettes, a masterbatch or tablets, is particularly suitable as a precursor for printing inks.

The present invention therefore also provides formulations comprising the pigment mixture of the invention.

The examples which follow are intended to illustrate the invention without, however, limiting it.

EXAMPLES Example 1 Paint

Formulations consisting of

2.50% Fe₂O₃-coated SiO₂ flakes having a particle size of 5-40 μm (Merck KGaA) 1.50% Monastral green 6Y spec. (Zeneca) 0.50% Cappoxyt yellow 4214 (Cappelle) 0.03% Pigment-grade carbon black FW 200 (Degussa) 0.40% Dollaraluminium Alpate 7620 NS (Alcan Toyo Europe)

Remainder: Paint base with 19% solids content (acrylate-melamine) and diluent mixture

Example 2 Intaglio printing

Printing ink consisting of

70 g of nitrocellulose-based binder from Gebrüder Schmidt, 95MB011, with solids content of about 20% 30 g of pigment, i.e. 15 g of Cromal IV (Eckart) AL 14-18 μm and 15 g of Fe₂O₃- coated SiO₂ flakes of particle size 5-40 μm 30 g of 1-ethoxy-2-propanol

Example 3 Plastic

1 kg of polystyrene granules are wetted uniformly in a tumble mixer with 5 g of adhesion agent. Then 35 g of Fe₂O₃-coated SiO₂ flakes of particle size 5-40 μm and 7 g of Iriodin® 121 TiO₂-coated mica pigment from Merck KGaA, Darmstadt, FRG with particle size 5-20 μm are added and the components are mixed for 2 minutes.

These granules are processed under customary conditions on an injection moulding machine to give small stepped plates measuring 4×3×0.5 cm. The small stepped plates are notable for their luster.

Example 4 Eyeshadow

Phase A 15.00% TiO₂-coated SiO₂ flakes of particle size 5-40 μm (Merck KGaA) 15.00% Timiron Super Blue (TiO₂-coated mica of particle size 10-60 μm from Merck KGaA) 49.50% Talc  7.50% Solanum Tuberosum (potato starch)  2.50% Magnesium stearate

Phase B 9.14% Isopropyl stearate 0.53% Cetyl palmitate 0.53% Petrolatum 0.21% Fragrance 0.11% Preservative

The constituents of Phase A are combined and formed into a premix. The melted phase B is then added dropwise with stirring to the powder mixture. The powders are pressed at 40-50 bar.

Example 5 Shower gel

Phase A 0.10% TiO₂-coated SiO₂ flakes of particle size 5-40 μm (Merck KGaA) 0.10% Timiron Super Blue (TiO₂-coated mica of particle size 10-60 μm from Merck KGaA) 0.75% Xantham gum ad 100.00% Aqua

Phase B 20.00% Decyl glycoside 6.65% Texapon ASV Sodium laureth sulfate Magnesium laureth sulfate Sodium laureth 8-sulfate Magnesium laureth 8-sulfate Sodium oleth sulfate 0.20% Preservative 0.05% Fragrance

Phase C 0.15% Citric acid 10.00% Aqua

For Phase A, the pigment is stirred into the water. The xanthan gum is scattered in slowly with stirring and the mixture is stirred until the gum has dissolved. Phases B and C are added in succession, and slow stirring is continued until all of the components are homogeneously distributed. 

What is claimed is:
 1. A pigment mixture comprising two different components A and B mixed in a weight ratio of A:B of from 1:10 to 10:1, wherein component A is SiO₂ flakes coated with one or more metal oxides and/or metals and component B is a special effect pigment comprising one or more of metal platelets optionally coated with one or more metal oxides, graphite platelets, optionally coated aluminum platelets, optionally coated Al₂O₃ flakes, Fe₂O₃ flakes, TiO₂ flakes, BiOCl, glass platelets and ceramic platelets.
 2. The pigment mixture of claim 1, wherein component A comprises a pigment of SiO₂ flakes coated with TiO₂ and/or Fe₂O₃.
 3. The pigment mixture of claim 1, wherein components A and B are mixed in a weight ratio of A:B of from 3:1 to 5:1.
 4. A paint, varnish, printing ink, powder coating, masterbatch, plastic, colored seed coating, cosmetic or food coloring enhancer comprising a pigment mixture according to claim
 1. 5. A composition comprising a pigment mixture according to claim 8 and a binder, wherein the composition is substantially solvent-free and in the form of free-flowing granules.
 6. The pigment mixture of claim 1, wherein the component B special effect pigment comprises optionally coated aluminum platelets.
 7. The pigment mixture of claim 1, wherein the component B special effect pigment comprises a gold/bronze alloy pigment.
 8. The pigment mixture of claim 1, wherein the component B special effect pigment comprises an optionally coated platelet-shaped iron oxide pigment, aluminum flakes or coated aluminum flakes.
 9. The pigment mixture of claim 1, wherein the component B special effect pigment comprises optionally coated Al₂O₃ flakes, graphite platelets, BiOCl or glass platelets.
 10. The pigment mixture of claim 1, wherein the component B special effect pigment comprises aluminum flakes or coated aluminum flakes.
 11. The pigment mixture of claim 1, wherein the component B special effect pigment comprises optionally coated Al₂O₃ flakes, BiOCl or glass platelets. 